This invention relates to the field of phase conjugate enhanced lasers having selectable output energy levels and selectable pulse repetition frequencies and also having fixed boresight axis alignment.
In many laser settings there exists a need for performing a manual positioning or alignment of the laser prior to the application of work achieving energy to the laser apparatus and to a selected workpiece area. Medical settings such as in the laser surgery commonly employed for detached retina repair and tumor removal, and laser weapon systems, are examples of laser uses which are benefitted by a multiple energy capability in the laser. In an airborne laser weapon system, for example, it is frequently necessary to calibrate or aim the weapon system while the host aircraft is located on a taxi strip or otherwise in the presence of personnel, friendly aircraft, and property. In such a scenario, the inability of the laser weapon system to function in a safe low energy operating mode, can represent both a hazardous and an inconvenient and energy-demanding limitation of the system. A multiple energy level laser apparatus is also desirable for industrial uses such as cutting, drilling, and welding, where common boresight and multiple energy level operation properties are useful in achieving the initial positioning and the subsequent heat generating functions.
Heretofore, the achievement of multiple output energy levels in a laser system has required the use of plural lasers that feed a common optical output apparatus from dispersed but precisely aligned physical locations. Clearly, the establishment and maintaining of such physically displaced but precisely aligned laser sources is inconvenient and a source of ongoing difficulty. The present apparatus circumvents this inconvenience by providing in a single laser source the capability for multiple output energy levels and multiple pulse repetition frequency operation.
In airborne avionic applications, a "very low" energy mode of laser operation is desirable for eye-safe boresighting of the laser apparatus with other avionics system components. In this environment, a greater energy level, "low energy" laser operating mode is also characteristic of optical search and related functions. Additionally, in this environment, "medium energy" modes of laser operation are desirable for weapon usage and other long-range functions. The presently-existing approach to satisfying these needs involves separate laser sources boresighted through common optics. Since the primary energy available in an avionic environment is limited, it is often not practical to operate for example three separate lasers simultaneously in a separate source, common optic boresighting arrangement. As a result, intermittent and transient operation of the individual laser sources must be considered--an arrangement which has warm-up stability and other disadvantages.
The most desirable existing technology for realizing a single laser having a variety of energy output formats includes the use of a multiple lamp cavity--an arrangement that is inefficient and limited in output power. Additionally, single lasers having multifunctional capability have not generally been compatible with techniques that allow efficient wavelength agility without being susceptible to a high risk of optical damage.